She uses the sword as a conduit to unlease devastating magical spells against the Lucifer Hawks. Grospoliner also provides Katsumi with advice and warns her of danger. Grospoliner was also wielded by Katsumi's father, Gigelf. However Katsumi surpasses her father's abilities, releasing much more devastating magic than he could. This may be partly due to the sorcerous abilities of her mother, Fuyaka.

Grospoliner is several hundred years old and has long memories, as well as his own personality. The TV series develops his personality a bit more than in the manga. He reminisces about the "good old days", as he can remember the time before the world was ravaged by the failed Project Gaia. He is also something of a philosopher and remarks on the state of the world. Things have changed greatly since he was imprisoned and much of it makes him sad, or even a little scared.